Why Affordable Soil Testing May Be Costing African Farmers More Than It Saves, Study Warns

A World Bank study in Uganda reveals that affordable soil-testing devices and digital soil maps often produce inaccurate results, risking poor fertilizer decisions, higher farming costs and reduced productivity. Researchers urge governments to combine innovative soil-testing technologies with laboratory validation to improve agricultural efficiency, protect farmers' incomes and strengthen food security across Sub-Saharan Africa.

A new World Bank study, conducted by researchers from the World Bank's Development Data Group, Kenyon College and The Ohio State University, using laboratory analysis from the Center for International Forestry Research and the International Centre for Research in Agroforestry (CIFOR-ICRAF), has raised concerns about the reliability of affordable soil-testing technologies in African agriculture. Published in November 2026, the research examines whether portable soil scanners, testing kits and digital soil maps can accurately measure soil fertility and help farmers make better agricultural decisions. Based on field evidence from Uganda, the study finds that although these technologies offer faster and potentially cheaper soil assessments, their results often differ significantly from laboratory measurements, creating risks for farmers, agricultural programmes and policymakers.

Declining soil fertility remains a major challenge across Sub-Saharan Africa, where millions of households depend on agriculture for income and food security. Poor soil conditions, limited fertilizer use and differences in soil quality between neighbouring farms contribute to low crop productivity. Accurate soil information can help farmers identify nutrient deficiencies, choose suitable fertilizers and improve yields. However, conventional laboratory testing remains costly and difficult to expand across remote farming communities, encouraging governments and development organizations to explore cheaper alternatives.

Uganda Study Exposes Gaps in Modern Soil Testing

To examine the effectiveness of these technologies, the World Bank launched the Uganda Climate, Land Area, and Soil Study (CLASS), covering five districts: Apac, Dokolo, Buyende, Kamuli and Kaliro. Conducted between August 2023 and March 2024, the research covered 75 enumeration areas and targeted 900 maize-growing households. Researchers collected soil samples, interviewed farmers and examined agricultural practices and crop yields.

The study compared three soil-testing devices—the AgroCares Scanner, Palintest kit and Sonkir pH meter—alongside two digital soil maps, iSDAsoil and SoilGrids. Their performance was assessed against laboratory-based measurements conducted by CIFOR-ICRAF. Researchers focused on five important soil characteristics: acidity, clay content, organic carbon, nitrogen and potassium.

One major finding was that farmers' perceptions of soil quality frequently differed from scientific measurements. Farmers commonly judged fertility through soil colour, crop yields, texture and vegetation. However, these observations showed weak relationships with measured soil properties. Some farmers described their land as good despite unfavourable soil conditions, while plots considered poor did not always show corresponding deficiencies.

Portable Soil Scanners Show Promise but Accuracy Remains Weak

Among the technologies examined, the AgroCares Scanner performed relatively well in measuring clay content, achieving a correlation of 0.68 with laboratory results. Its performance was weaker for organic carbon and nitrogen, with correlations of 0.45 and 0.43, respectively. However, its measurements of soil acidity and potassium showed little agreement with laboratory estimates.

The Palintest kit performed better in measuring soil acidity, recording a correlation of 0.54 with the benchmark. Nevertheless, it frequently underestimated lower pH values and overestimated higher ones. The inexpensive Sonkir pH meter performed particularly poorly, producing unreliable measurements despite offering immediate results.

Digital soil maps also demonstrated serious limitations. Although iSDAsoil generally performed better than SoilGrids, both frequently assigned similar soil characteristics to agricultural plots with substantially different laboratory measurements. Their inability to capture local variations raises questions about their suitability for recommending fertilizers and soil treatments at the individual farm level.

Inaccurate Soil Data Could Increase Costs for Farmers

The research highlights how incorrect soil measurements can translate into costly agricultural decisions. When researchers classified soils into categories used for fertilizer and soil management recommendations, Palintest matched laboratory acidity classifications for only approximately 54% of samples. AgroCares achieved 68% agreement for clay content and 53% for organic carbon.

Such differences could encourage farmers to apply unnecessary fertilizers, purchase unsuitable soil amendments or overlook important nutrient deficiencies. These mistakes could increase production expenses, reduce expected crop improvements and weaken confidence in agricultural advisory services.

The study also identified significant differences in testing costs. Laboratory spectroscopy cost approximately $12 per sample, compared with $27 for Palintest and $41 for AgroCares under the study's operating conditions, excluding certain additional expenses. AgroCares required an initial equipment investment of approximately $7,000 and annual licensing fees between $1,800 and $2,600. However, its rapid results and potential for lower average costs when processing larger numbers of samples could make it attractive for large-scale agricultural programmes.

Governments Urged to Balance Innovation with Reliable Testing

The findings carry important implications for governments seeking to improve agricultural productivity, fertilizer efficiency and climate resilience. Soil-testing technologies could help policymakers identify areas requiring intervention, but inaccurate information may result in poorly targeted subsidies, wasted agricultural inputs and ineffective soil restoration programmes.

Researchers recommend combining portable testing technologies and digital mapping systems with regular laboratory validation. Testing selected soil samples through accredited laboratories would help identify measurement errors and improve the reliability of agricultural recommendations.

The study concludes that no single technology currently offers an ideal combination of accuracy, affordability, speed and scalability across all soil characteristics. While portable scanners and digital maps could improve access to agricultural information, their limitations must be understood before widespread adoption.

For farmers, reliable soil testing could mean lower input costs, better fertilizer choices and improved crop productivity. For policymakers, the challenge is to ensure that investments in agricultural technology produce dependable information rather than simply faster results. Strengthening soil monitoring through scientifically validated approaches will be essential for protecting rural livelihoods, improving food security and supporting sustainable agriculture across Sub-Saharan Africa.